Help with matrix transpose

hi i have a program that compiles and works
it scans points from a txt file (that i attached) into a 2D matrix and from this matrix i calculated and generated the matrix 'A' . Now i need to transpose this A matrix

i was given this subroutine in my linear_algebra.h library to find the transpose of a matrix

Code:

---

// Transposition.
void matrix_transpose(double m1[], double mr[], int h, int w)
{
  int i, j;

  for(i = 0; i < h; ++i)
    for(j = 0; j < w; ++j)
      mr[in2d(j, i, h)] = m1[in2d(i, j, w)];

  return;
}

---

but it doesnt work....

I need to print the transpose of my A matrix
please help

heres my program
and i attached the linear algebra library that i was provided which has the transpose subroutine in it

Code:

---

#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include "linear_algebra.h"


int main(){
        int n,i,j;
  double **a;    /* this is the array of points name */
        double **A;        /* this is the array of 2n x 9*/
        double **At; /* this is the array of A transpose */
        int num_rows; /* this variable will be used for the first  dimension */
  int num_col; /* this variable will be used for the second dimension */

        FILE * ifile;
  ifile = fopen ("points.txt","r");
        fscanf(ifile, "%d\n", &n);/*read in the number of points N.*/
        printf("%d\n", n);

  num_rows = n;
  num_col = 6;

  /*  allocate storage for an array of pointers */
  a = malloc(num_rows * sizeof(double *));

  /* for each pointer, allocate storage for an array of doubles */
  for (i = 0; i < num_rows; i++) {
    a[i] = malloc(num_col * sizeof(double));
  }

  /* assign the value to each element        */
  for (i = 0; i < num_rows; i++) {
    for (j = 0; j < num_col; j++) {
      fscanf(ifile,"%lf ", &a[i][j]);
    }
  }

        /*  malloc again for 2nd array */
  A = malloc((2*n) * sizeof(double *));

  for (i = 0; i < (2*n); i++) {
    A[i] = malloc(9 * sizeof(double));
  }


        /* create a 2*n X 9 matrix*/
        for (i = 0; i < num_rows; i++) {
  A[2*i][0]=0;
  A[2*i][1]=0;
  A[2*i][2]=0;
  A[2*i][3]=(-a[i][5])*a[i][0];
  A[2*i][4]=(-a[i][5])*a[i][1];
  A[2*i][5]=(-a[i][5])*a[i][2];
  A[2*i][6]=(a[i][4])*a[i][0];
  A[2*i][7]=(a[i][4])*a[i][1];
  A[2*i][8]=(a[i][4])*a[i][2];

  A[2*i+1][0]=(a[i][5])*a[i][0];
  A[2*i+1][1]=(a[i][5])*a[i][1];
  A[2*i+1][2]=(a[i][5])*a[i][2];
  A[2*i+1][3]=0;
  A[2*i+1][4]=0;
  A[2*i+1][5]=0;
  A[2*i+1][6]=(-a[i][3])*a[i][0];
  A[2*i+1][7]=(-a[i][3])*a[i][1];
  A[2*i+1][8]=(-a[i][3])*a[i][2];
        }


/*  malloc again for 3rd array */
  At = malloc((2*n) * sizeof(double *));

  for (i = 0; i < (2*n); i++) {
    At[i] = malloc(9 * sizeof(double));
  }



        for (i = 0; i < 2*n; i++) {
    for (j = 0; j < 9; j++) {
 printf("%6.4lf ", A[i][j]);
    }
  }




        /* now for each pointer, free its array of dbles */
  for (i = 0; i < num_rows; i++) {
    free(a[i]);
  }
  /* now free the array of pointers */
  free(a);

        /* free for 2nd array */
  for (i = 0; i < (n*2); i++) {
    free(A[i]);
  }

  free(A);

/* free for 3rd array */
  for (i = 0; i < (n*2); i++) {
    free(At[i]);
  }

  free(At);

        fclose(ifile);
        return 0;
}

---

The given procedure works with linear array as if it stores the matrix
the function
in2d(j, i, h) just retreives the index in the linear array based on the row/col numbers and row width

In your case the Matrixes are stored in the 2-dimentional array
so you can just do
At[i][j] = A[j][i]
for all i,j needed

thanx alot...
would u kno how to multiply A by At by any chance?

do you have a formula? have you tried to program it? Could you post your attemp result?

this is the formula but it has the in2d again

Code:

---

/ Multiplication.
// Need (wm1 == hm2) && (hm1 == hmr) && (wm2 == wmr).
void matrix_mult(double m1[], double m2[], double mr[],
  int hm1, int wm1, int wm2)
{
  int i, j, k;
  double sum;

  for(i = 0; i < hm1; ++i)
    for(j = 0; j < wm2; ++j) {
      sum = 0;
      for(k = 0; k < wm1; ++k)
        sum += m1[in2d(i, k, wm1)] * m2[in2d(k, j, wm2)];

      mr[in2d(i, j, wm2)] = sum;
    }

  return;
}

---

i tried to change the code like you did last time and i did this but it doesnt work

Code:

---


  /*matrix multiplication*/


  for(i = 0; i < 9; i++){
    for(j = 0; j < 9 ; j++) {
      for(k = 0; k < 2*n; k++){

      W[i][j]+= (A[i][k])*(At[k][j]);
    }
  }
}

---

ok and heres my whole program...if you take out the multiplication it works so far

Code:

---

#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include "linear_algebra.h"


int main(){
        int n,i,j,k;
  double **a;    /* this is the array of points name */
        double **A;        /* this is the array of 2n x 9*/
        double **At; /* this is the array of A transpose */
        double **W; /*this is the 9 x 9 arrray*/
  int num_rows; /* this variable will be used for the first  dimension */
  int num_col; /* this variable will be used for the second dimension */

        FILE * ifile;
  ifile = fopen ("points.txt","r");
        fscanf(ifile, "%d\n", &n);/*read in the number of points N.*/
        printf("%d\n", n);

  num_rows = n;
  num_col = 6;

  /*  allocate storage for an array of pointers */
  a = malloc(num_rows * sizeof(double *));

  /* for each pointer, allocate storage for an array of doubles */
  for (i = 0; i < num_rows; i++) {
    a[i] = malloc(num_col * sizeof(double));
  }

  /* assign the value to each element        */
  for (i = 0; i < num_rows; i++) {
    for (j = 0; j < num_col; j++) {
      fscanf(ifile,"%lf ", &a[i][j]);
    }
  }

        /*  malloc again for 2nd array */
  A = malloc((2*n) * sizeof(double *));

  for (i = 0; i < (2*n); i++) {
    A[i] = malloc(9 * sizeof(double));
  }


        /* create a 2*n X 9 matrix*/
        for (i = 0; i < num_rows; i++) {
  A[2*i][0]=0;
  A[2*i][1]=0;
  A[2*i][2]=0;
  A[2*i][3]=(-a[i][5])*a[i][0];
  A[2*i][4]=(-a[i][5])*a[i][1];
  A[2*i][5]=(-a[i][5])*a[i][2];
  A[2*i][6]=(a[i][4])*a[i][0];
  A[2*i][7]=(a[i][4])*a[i][1];
  A[2*i][8]=(a[i][4])*a[i][2];

  A[2*i+1][0]=(a[i][5])*a[i][0];
  A[2*i+1][1]=(a[i][5])*a[i][1];
  A[2*i+1][2]=(a[i][5])*a[i][2];
  A[2*i+1][3]=0;
  A[2*i+1][4]=0;
  A[2*i+1][5]=0;
  A[2*i+1][6]=(-a[i][3])*a[i][0];
  A[2*i+1][7]=(-a[i][3])*a[i][1];
  A[2*i+1][8]=(-a[i][3])*a[i][2];
        }


/*  malloc again for 3rd array */
  At = malloc((2*n) * sizeof(double *));

  for (i = 0; i < (2*n); i++) {
    At[i] = malloc(9 * sizeof(double));
  }


/* matrix transpose*/
        for (i = 0; i < 2*n; i++) {
    for (j = 0; j < 9; j++) {
  At[i][j]=A[j][i];

    }
  }


/*  malloc again for 4th array */
  W = malloc((9) * sizeof(double *));

  for (i = 0; i < (9); i++) {
    W[i] = malloc(9 * sizeof(double));
  }


  /*matrix multiplication*/


  for(i = 0; i < 9; i++){
    for(j = 0; j < 9 ; j++) {
      for(k = 0; k < 2*n; k++){

      W[i][j]+= (A[i][k])*(At[k][j]);
    }
  }
}

for (i = 0; i < 9; i++) {
    for (j = 0; j <9 ; j++) {
printf("%6.4lf ", W[i][j]);
    }
  }
        /* now for each pointer, free its array of dbles */

  for (i = 0; i < num_rows; i++) {
    free(a[i]);
  }
  /* now free the array of pointers */
  free(a);

        /* free for 2nd array */
  for (i = 0; i < (n*2); i++) {
    free(A[i]);
  }

  free(A);

/* free for 3rd array */
  for (i = 0; i < (9); i++) {
    free(At[i]);
  }

  free(At);
/* free for 4th array */
  for (i = 0; i < (9); i++) {
    free(W[i]);
  }

  free(W);

  fclose(ifile);
        return 0;
}

---

W[i][j]+= (A[i][k])*(At[k][j]);
you should iitialize W[i][j] before entering the loop, otherwise the result will contain garbage

thank you so much u helped me alot